New modes of Doppler ultrasound and new signal conditioning of the received sonic spectrum permit accurate assessment of mean and peak velocities of blood flow. New systems will, in the near future, permit quantitation of the entire flow field velocities. Three studies using these technologies have been completed: (1) quantification of obstruction and regurgitation in right ventricular to pulmonary artery conduits with and without prosthetic valves; (2) quantification of aortic insufficiency; and (3) correlation of pressure drops across stenotic bioprosthetic valves in the mitral and tricuspid position. The results show that high correlations of pressure drop by Doppler measurements to those measured simultaneous by traditional methods. Contrast echocardiography was successful in quantitation of aortic insufficiency. This noninvasive system has been used to determine the degree of regurgitation and obstruction in two patients to date.